Field of the Invention
The present invention relates to a resin fine particle and a method of producing a resin particle including using the resin fine particle, and more particularly, to a method of producing a toner to be used in a recording method involving utilizing an electrophotographic method, an electrostatic recording method, and a toner jet type recording method.
Description of the Related Art
Resin particles have been utilized as powder having a high function in a wide variety of fields, and monodisperse resin particles having a narrow particle size distribution have been required in many cases in order to control the function. Particularly in the field of electrophotography, the particles of a toner forming an image need to have uniform performance because the particles has a significant influence on an improvement in quality of the image. To that end, the uniformization of the particle diameters of the toner particles to sharpen their particle size distribution and the suppression of the occurrence of a deformed particle having a low circularity are effective.
A “dissolution suspension method” has been known as a production method capable of easily achieving the sharpening of the particle size distribution of the toner particles and increases in their circularities. The dissolution suspension method is a method involving dispersing a resin solution, which is obtained by dissolving a resin in an organic solvent in advance, in a dispersion medium to form droplets of the resin solution, and then removing the organic solvent to provide the toner particles.
In the dissolution suspension method, an aqueous medium is generally used as the dispersion medium. However, when the aqueous medium is used, large amounts of energy and time are required in a washing step and a drying step after the formation of the particles. Accordingly, in recent years, a method of producing a toner involving using carbon dioxide as a dispersion medium has been proposed.
In the method, toner particles are obtained by performing, after a droplet-forming step of forming a dispersion of droplets based on a resin solution in carbon dioxide in a liquid or supercritical state, a desolvating step of further introducing carbon dioxide to extract and remove an organic solvent in the droplets. According to the method, the resultant toner particles can be easily separated from carbon dioxide serving as the dispersion medium by depressurization after the desolvating step. Accordingly, a washing step and a drying step are not required, and hence the toner can be produced with low energy and at a low cost.
In the production of the toner by the dissolution suspension method involving using carbon dioxide as the dispersion medium, a dispersant needs to be used in the droplet-forming step for achieving the sharpening of the particle size distribution of the toner and an increase in its circularity. The dispersant plays the following role. The dispersant covers the surfaces of the droplets of the resin solution to suppress the agglomeration and sedimentation of the droplets, thereby stably dispersing the droplets, and the dispersant maintains their dispersed states till the end of the desolvating step. Therefore, the selection of the dispersant is extremely important.
In Japanese Patent Application Laid-Open No. 2009-052005 and Japanese Patent Application Laid-Open No. 2010-132851, there is proposed a method of producing a resin particle involving utilizing carbon dioxide in a liquid or supercritical state as a dispersion medium and using a resin fine particle as a dispersant. In Japanese Patent Application Laid-Open No. 2009-052005, a resin fine particle formed of behenyl acrylate and a methacryl-modified silicone is used.
In Japanese Patent Application Laid-Open No. 2010-132851, a crystalline resin fine particle made of, for example, a polyester or a behenyl acrylate copolymer is used.
In Japanese Patent Application Laid-Open No. 2013-137535, there is proposed a toner produced by using a resin fine particle containing a resin having a graft type structure constituted of a moiety having an organic polysiloxane structure and a moiety having an aliphatic polyester structure in a dispersion medium containing carbon dioxide.
According to the method, toner particles having a satisfactory particle size distribution can be obtained under a temperature as low as about 25° C. because the resin fine particle has a structure having affinities for both carbon dioxide and a resin solution.